Lubricating oil additive and oil containing the same having improved water tolerance



LUBRICATING OIL ADDITIVE AND OIL CON- TAINING TIE SAME HAVING HVIPROVED WATER TOLERANCE Harvey E. Alford, Amherst, and Chien-Wei Liao, Cleveland, Ohio, assignors to The Standard Oil Company, 1

Cleveland, Ohio, a corporation of Ohio No Drawing. Application December 24, 1956 Serial No. 630,051 4 Claims. (Cl. 252-18) This invention relates to lubricating oil additives useful in the preparation of lubricating oil having a lessened or substantially no tendency to form cold sludge and, more particularly, to lubricating oil compositions containing an alkaline detergent, an antioxidant, and a phosphorusand sulfur-containing polymer.

When an engine is operated during cold weather and in light duty stop-and-go operations, it rarely is heated to operating temperature for any substantial portion of the driving time. When the temperatures in the crank case are below operating temperatures, contaminants enter the crankcase by way of blow-by. These contaminants are not dissipated because of the low operating temperatures of the oil, and have an opportunity to react or to catalyze reactions in the oil. These reactions result in the formation of what is called cold sludge, a black, mayonnaise-like substance. One of the most important problems today is how to combat cold sludge, because most cars used in city driving are subjected to this type of driving conditions during cold weather.

It has now been determined that when oil containing an alkaline sulfonate-type detergent and a thiophosphate-type antioxidant as additives has added thereto a phosphorusand sulfur-containing polymer, the oil does not develop cold sludge when the engine is operated at low temperatures for long periods of time. It is thought that this combination of additives is effective because the lubricating oil containing the additive has a marked increase in water tolerance, a property which is of particular importance in connection with the formation of cold sludge.

The alkaline sulfonate-type detergent and the thiophosphate-type antioxidants are well known in the lubricating oil additive art. The preferred alkaline sulfonatetype detergent is formed from barium octadecyl-sulfonate and barium carbonate. This additive is well known and needs no further description. The barium carbonate is thought to neutralize the acids that are formed. The preferred antioxidant is zinc octyl dithiophosphate which has a molecular Weight of about 321.4 and has the formula ZnC H PS(S) It is the zinc salt of a phosphorus pentasulfide-octyl mercaptan reaction product. The zinc octyldithiophosphate is an antioxidant and, in addition, inhibits corrosion and Wear.

The phosphorusand sulfur-containing polymer has a complex structure which is defined as follows:

where R is an alkyl radical or a plurality of alkyl radicals having in total from one to three carbon atoms, R is an alkenyl radical of the type C H where n has the value of eight to twenty-two, x has a value within the range from two to ten, X is selected from the group consisting of sulfur and oxygen, and at least one X is oxygen, and M is an alkali metal such as potassium, so-

'ice

2 dium, or lithium. Thus, the R radicals can be methyl, ethyl, propyl, and isopropyl, and there can be from one to three methyl radicals or one methyl and one ethyl radical. The C H radical can be, for instance, dodecenyl, hexadecenyl, pentadecenyl, octadecenyl, and nonenyl, either straight or branched. The long chain alkenyl radical is necessary in order to solubilize the condensation product in petroleum lubricating oils. The polymeric nature of this compound has been found to function as a viscosity index improver. In addition, the presence of the metal imparts detergency and the group imparts antioxidant properties.

These compounds can be prepared by reacting an olefin of the type formula C H with phosphorus pentasulfide at an elevated temperature with nitrogen stripping. Hydrogen sulfide is evolved in the reaction. The resulting product is the alkenyl trithiophosphonic thioanhy- This material is reacted with an alkali metal hydroxide to prepare an alkali metal alkeuyldithiophosphonate:

This is separated from the excess olefin resulting from the first reaction by reacting it with a slight excess of an alkali metal hydroxide and extracting the soluble thiophosphonate with water. The aqueous solution is then acidified with a mineral acid, such as hydrochloric or sulfuric acid, and extracted with ether. The product is recovered by neutralizing the ether solution with an alcoholic alkali metal hydroxide and vacuum stripping:

(n l)R-;(OM): (MCICH; CHzCl Miaaacaoalaaxn L t l t I A preferred embodiment of the polymer has the formula:

Reference is made to application Serial No. 630,050,

scription of the product and process of preparing the s? polymer. All of such as is necessary is incorporated herein by reference.

Very small amounts of the additives of the invention will give a marked improvement in lessening the formation of cold sludge. As little as 1.0% of the total mixture of all the additives is effective, and amounts between 2% and 7% are preferred. Use of amounts in excess of 20% usually cannot be justified economically. The polymer is present in said total mixture in an amount within the range of 0.1 to 5 parts by weight (p. b. w.). The other three ingredients are combined in a mixture in the proportions of 20 to 60 p. b. W. barium octadecyl sul fonate, 10 to 30 p. b. w. barium carbonate, and to 45 p. b. W. zinc octyldithiophosphate. This mixture is employed in said total mixture in an amount of l to 10 p. b. w., preferably about 2 to 5 p. b. w.

The additives of the invention can be used to improve the cold sludge characteristics of any petroleum hydrocarbon oil of lubricating viscosity. The S. A. E. viscosities for lubricating oils range from No. 10 to No. 70. Oils having S. A. E. Nos. 10 to 40 have a viscosity within the range from 90 to 225 SSU at 130 F., and those oils having S. A. E. Nos. 40 to 70 have a viscosity within the range from 80 to 150 SSU at 210 F. The acid-treated and solvent-extracted Oils are equally useful in the compositions of the invention. The oils can be blended from finished neutral oils of light and heavy viscosities and can include suitable bright stocks. It can also include other conventional additives such as V. I. improvers. It is impossible here to give a complete description of the various methods used in the preparation of lubricating oils, but reference is made to the text by Georgi, entitled Motor Oils and Engine Lubrication, published by Reinhold Publishing Corporation, New York (1950), chapter V, wherein the various types 35 of lubricating oils are discussed fully. Any of the oils mentioned therein can be employed in the composition of the invention.

The composition of the invention is prepared simply by mixing the additives, either singly or together, with the oil, at room temperature. The additives are soluble or dispersible in the oil, and disperse therein instantaneously. No solvents are required but the additives can be placed in solution in a hydrocarbon.

The following examples represent, in the opinion of the inventors, the best embodiment of their invention.

EXAMPLE (1) A solution was prepared containing 2.25% by weight of a mixture of 40 p. b. w. barium octadecylsulfonate, molecular weight 783.4, formula 3 18 27)2 p. b. W. barium carbonate, and 28 p. b. w. zinc octyldithiophosphate ZnC H PS(S) molecular Weight p 321.4, in solvent-extracted neutral oil, 140 SSU at 210 F.

(2) A solution was prepared containing 1% of the polymer (1) in the same solvent extracted neutral oil.

(3) A solution was prepared containing 2.25% of the mixture described under (1) above and 1% of the polymer described under (2) above. These three solutions were 0 tested for dispersancy and water tolerance with the following results:

Table l A consideration of the above results will reveal a synergistic eifect between the two ingredients when tested.

by the Water tolerance test.

The dispersancy test is a measure of the ability of the oil to hold carbon black dispersed. The oil to be tested is made up as a 5% solution thereof in benzene, and 100 ml. of the solution is placed in a glass stoppered graduate. Carbon black in increments of 0.2 gm. is added to the solution, which is then shaken for fifteen seconds and permitted to stand for five minutes in front of a light source and the contents observed for a break point. This point is seen as a thin upper layer of completely transparent liquid containing no carbon black particles. If no break point is observed, additional increments of carbon black are added until there is a break point.

The lar est amount of carbon black which does not produce a break point is recorded as the result of the test. The test has been calibrated against various additive concentrations of dispersant additives in oil and is a measure of the dispersant or detergent properties of an oil.

The water tolerance test is an extension of the test previously described, and the solution of the oil is made up in the same way and has added to it an amount of carbon black equal to the dispersancy rating. Distilled water is then added in 10 ml. increments, and after each addition the graduate is stoppered and shaken for fifteen seconds and allowed to stand five minutes. After this time, the suspension is similarly observed for a break point, and if none is observed an additional 10 m1. of water is added. This is continued until a break point is noted. The water tolerance test is important since an additive must not only have dispersant action in a dry oil but also in the presence of Water, because a crankcase in the winter often contains water as a result of condensation.

Other modifications of the invention will be obvious to one skilled in the art within the scope of the following claims.

We claim:

1. A mineral lubricating oil additive comprising (1) from 1.0 to 10 parts by weight of a mixture consisting essentially of 20 to 60 parts by weight of barium octadecylsulfonate, from 10 to 30 parts by weight of barium carbonate, and from 15 to parts by Weight of zinc cctyldithiophosphate, and (2) 0.1 to 5 parts by weight of a polymer having the structure:

within the range from two to ten and represents the.

average number of such units in the molecule.

2. A mineral lubricating oil additive in accordance with claim 1 in which in the formula therein R is the hexadecenyl radical, all of the X atoms are oxygen, and M is potassium.

3. A mineral lubricating oil containing from 1 to 20% of the additive of claim 1.

4. A mineral lubricating oil containing from 1 to 20% ofthe additive of claim 2.

References Cited in the file of this patent UNITED STATES PATENTS Mikeska et al Feb. 18, 1947 Mertes Mar. 28, 1950 

1. A MINERAL LUBRICATING OIL ADDITIVE COMPRISING (1) FROM 1.0 TO 10 PARTS BY WEIGHT OF A MIXTURE COMPRISING ESSENTIALLY OF 20 TO 60 PARTS BY WEIGHT OF BARIUM OCTADECYLSUFONATE, FROM 10 TO 30 PARTS BY WEIGHT OF BARIUM CARBONATE, AND FROM 15 TO 45 PARTS BY WEIGHT OF ZINC OCTYLDITHIOPHOSPHATE, AND (2) 0.1 TO 5 PARTS BY WEIGHT OF A POLYMER HAVING THE STRUCTURE: 